For example, Japanese Patent Laying-Open No. 2007-018013 (PTD 1) discloses a display device which increases the amount of light from a light source for illumination when an input signal has a high brightness, and decreases the amount of light from the light source for illumination when the input signal has a low brightness. In addition, Japanese Patent Laying-Open No. 2008-309908 discloses an image display device which raises the level of a video signal or the level of brightness when the level of the video signal is low for more than a certain time.